This invention relates generally to the use of a conical device to accurately obtain the center of square stock turned in a lathe. More specifically, it relates to a fixture that has v-shaped grooves inside the fixture, with these grooves also acting as the means to center the stock that is to be turned.
Wood turning lathes are used for the manufacture of chair and table legs, stairway ballisters, and other spindles. In the making of these spindles, it is desirable to have decorative designs on the spindle. It is imperative, therefore to obtain the center of the stock and to hold the stock at that center throughout the turning of stock. It is further desirable to have a centering device that does not cut into the stock which may cause the stock to split. Finally, it is advantageous to have a centering device that is versatile in its use that it may accept any type or size of stock. The present invention with its cone, or more specifically, centering heads will accept a wide variety of sizes without the need to have many, expensive heads to hold stock of varying sizes.
Prior centering fixtures did not have the versatility to accept all sizes of stock without multiple, expensive pieces. Also, these prior fixtures harmed or may have split the stock, possibly making the stock not usable for its intended purpose. Further, previous centering devices did not center using the corners of the stock, thus they did not ensure an accurate center. Some specific examples of the prior art problems that are solved by the present invention are that when a square piece of stock is placed in a cone with protruding blades, such as shown by the Gardiner patent (U.S. Pat. No. 60,169, dated Dec. 4, 1866), there is no assurance that the stock at once be siezed in the center of the conical body as is argued in cited patent, or that the center of the stock has been achieved at both ends of the stock in the lathe. When the stock is pushed on the blades, they hold the stock and may split or otherwise harm the stock. Another example of prior art problems solved by this invention is that the prior centering fixtures were limited in sizes of stock that could be used. The prior art, as shown in the Hagquist patent (U.S. Pat. No. 3,272,611, dated Sep. 20, 1966), centered using specific varying levels that only stock specifically of the same size of those levels would obtain accurate centers. A final problem solved by the present invention lies in the prior art using the sides of the stock to center, as patented by Davis (U.S. Pat. No. 935,143, dated Sep. 28, 1909). These prior devices had adjustable holders tightened by set screws that were to tighten down on the sides of the stock. Because these were adjustable, there was no guarantee an accurate center had been achieved, as each side could not conceivably be adjusted in the exact same increments.
The present centering fixture solves these problems by using two fixtures, one on the head stock and one on the tail stock of the lathe. Because these two fixtures are identical, they both hold the stock at the same center. Also, the centering fixtures are conical with interior grooves to accept near universal sizes of stock. Further, because of these grooves, the present invention passively accepts and holds the stock in these grooves rather than actively cutting into the stock.